SB Acoustics Satori MR13P-4:
Klippel analysis for the MR13P-4 produced the Bl(X), Kms(X), and Bl and Kms symmetry range plots given in Figures 5–8. The Bl(X) curve (see Figure 5) is fairly symmetrical with some obvious coil-in offset. Looking at the Bl symmetry plot (see Figure 6), this curve shows a minor coil rearward (coil in) offset at the 2 mm position (a point of reasonable certainty) of 0.76 mm that is fairly constant out to the MR13P-4’s physical Xmax, so its likely just a small coil in offset, that easily could be deliberate. Note that the data at rest has a fair degree of uncertainty (the expanding grey area indicates the level of uncertainty of the graph), but a high degree of certainty at the 3 mm position. Figure 7 and Figure 8 show the Kms(X) and Kms symmetry range curves for the SB MR13P-4. The Kms(X) curve looks rather symmetrical in both directions with some minor offsets in the coil position as reflected in the Kms symmetry range curve. The coil- in offset displayed in the Kms symmetry range curve is 0.26 mm at the MR13P-4’s physical Xmax, so both Bl and compliance are well balanced even if this was a woofer operating in its piston range. Displacement limiting numbers calculated by the Klippel analyzer for the MR13P-4 were XBl @ 82% Bl = 3mm and for XC at 75% Cms minimum greater than 4 mm, which means that for the MR13P-4, if the driver was operating in the piston range, which it will likely not be, the Bl was the limiting factor for a distortion level of 10%, and it was equal to the driver’s physical Xmax.
Figure 9 gives the MR13P-4’s inductance curves L(X). The curve indicates an increasing inductance as the coil moves inward, however, there is only a minor change in inductance throughout the MR13P-4’s operating range—a key to its low distortion performance is the motor’s copper shorting ring (Faraday shield). Inductance change from the rest position to the Xmax coil-out position was 0.012 mH, and 0.016 mH to the Xmax coil-in position—which is excellent performance if it were a woofer, which it’s not.
Scan-Speaks 12MU/473100:
Klippel analysis for the Scan 12MU midrange produced the Bl(X), Kms(X) and Bl and Kms Symmetry Range plots given in Figures 5 to 8. The Bl(X) curve for the 12MU (see Figure 5) is moderately broad and very symmetrical, which is more like a woofer than a midrange. Looking at the Bl symmetry range curve in Figure 6, there is a 0.5-mm rearward (coil-in) offset that goes to 0 mm at the physical Xmax position (3.5 mm for the 12MU). Figure 7 and Figure 8 give the Kms(X) and Kms symmetry range curves for the12MU. The Kms(X) curve also is very symmetrical. However since the application is as a midrange that will always have a band-pass filter, excursion will be limited, regardless of how good the Klippel data for this driver looks. Even considering this, the forward coil-out offset at rest is only 1.5 mm resolving to 0 mm at about 3 mm of travel. Displacement limiting numbers calculated by the Klippel analyzer for the Scan midrange were XBl @ 82% Bl = 6.1 mm and for XC @ 75% Cms minimum was 4.8 mm, which means that for this 4" mid, the compliance is the most limiting factor for prescribed distortion level of 10%. Regardless, it is still significant that both XBl and XC numbers occur beyond the physical Xmax. The 12MU may be offered as a midrange, but it’s really not so bad as a woofer! Figure 9 gives the inductance curves Le(X) for the 12MU/4731T00, which shows a very small 0.15-mH inductance change across the operating range, again due to the copper shorting ring and overall motor construction.
Wavecor WF120BD04:
Klippel analysis for the Wavecor 4.75� woofer produced the Bl(X), Kms(X) and Bl and Kms symmetry range plots given in Figs. 22-25. The Bl(X) curve for the WF120 (Fig. 22) is relatively broad and symmetrical, especially for a 4.75� diameter driver, and obviously also with “tilt�? that includes a small forward (coil-out) offset. Looking at the Bl symmetry plot (Fig. 23), this curve shows a 0.8mm coil forward offset at the rest position that decreases to 0mm at the physical 4mm Xmax of the driver. Figures 24 and 25 show the Kms(X) and Kms symmetry range curves for the Wavecor midbass woofer.
The Kms(X) curve definitely has some asymmetry, and also with a minor rearward (coil-in) offset of about 0.8mm at the rest position that decreases to 0.25mm at the 4mm Xmax location on the graph, and increasing somewhat out to 6mm or so. While these numbers are small, it does limit the distortion levels somewhat. Displacement limiting numbers calculated by the Klippel analyzer were XBl at 82% Bl greater than 4.3mm and for XC at 75% Cms minimum was 2.3mm, which means that for this Wavecor woofer, the compliance is the most limit- ing factor for prescribed distortion level of 10%. This isn’t that much of an issue, especially because this woofer could easily find itself working as a midrange in a three-way product.
Figure 26 gives the inductance curve Le(X) for the WF120BD04. Inductance will typically increase in the rear direction from the zero rest position as the voice coil covers more pole area; however, the WF120 inductance stays most- ly constant as the coil moves in due to the dual shorting ring configuration. The inductance variation is only 0.05mH from the in and out Xmax positions, which is very good.
Klippel analysis for the MR13P-4 produced the Bl(X), Kms(X), and Bl and Kms symmetry range plots given in Figures 5–8. The Bl(X) curve (see Figure 5) is fairly symmetrical with some obvious coil-in offset. Looking at the Bl symmetry plot (see Figure 6), this curve shows a minor coil rearward (coil in) offset at the 2 mm position (a point of reasonable certainty) of 0.76 mm that is fairly constant out to the MR13P-4’s physical Xmax, so its likely just a small coil in offset, that easily could be deliberate. Note that the data at rest has a fair degree of uncertainty (the expanding grey area indicates the level of uncertainty of the graph), but a high degree of certainty at the 3 mm position. Figure 7 and Figure 8 show the Kms(X) and Kms symmetry range curves for the SB MR13P-4. The Kms(X) curve looks rather symmetrical in both directions with some minor offsets in the coil position as reflected in the Kms symmetry range curve. The coil- in offset displayed in the Kms symmetry range curve is 0.26 mm at the MR13P-4’s physical Xmax, so both Bl and compliance are well balanced even if this was a woofer operating in its piston range. Displacement limiting numbers calculated by the Klippel analyzer for the MR13P-4 were XBl @ 82% Bl = 3mm and for XC at 75% Cms minimum greater than 4 mm, which means that for the MR13P-4, if the driver was operating in the piston range, which it will likely not be, the Bl was the limiting factor for a distortion level of 10%, and it was equal to the driver’s physical Xmax.
Figure 9 gives the MR13P-4’s inductance curves L(X). The curve indicates an increasing inductance as the coil moves inward, however, there is only a minor change in inductance throughout the MR13P-4’s operating range—a key to its low distortion performance is the motor’s copper shorting ring (Faraday shield). Inductance change from the rest position to the Xmax coil-out position was 0.012 mH, and 0.016 mH to the Xmax coil-in position—which is excellent performance if it were a woofer, which it’s not.
Scan-Speaks 12MU/473100:
Klippel analysis for the Scan 12MU midrange produced the Bl(X), Kms(X) and Bl and Kms Symmetry Range plots given in Figures 5 to 8. The Bl(X) curve for the 12MU (see Figure 5) is moderately broad and very symmetrical, which is more like a woofer than a midrange. Looking at the Bl symmetry range curve in Figure 6, there is a 0.5-mm rearward (coil-in) offset that goes to 0 mm at the physical Xmax position (3.5 mm for the 12MU). Figure 7 and Figure 8 give the Kms(X) and Kms symmetry range curves for the12MU. The Kms(X) curve also is very symmetrical. However since the application is as a midrange that will always have a band-pass filter, excursion will be limited, regardless of how good the Klippel data for this driver looks. Even considering this, the forward coil-out offset at rest is only 1.5 mm resolving to 0 mm at about 3 mm of travel. Displacement limiting numbers calculated by the Klippel analyzer for the Scan midrange were XBl @ 82% Bl = 6.1 mm and for XC @ 75% Cms minimum was 4.8 mm, which means that for this 4" mid, the compliance is the most limiting factor for prescribed distortion level of 10%. Regardless, it is still significant that both XBl and XC numbers occur beyond the physical Xmax. The 12MU may be offered as a midrange, but it’s really not so bad as a woofer! Figure 9 gives the inductance curves Le(X) for the 12MU/4731T00, which shows a very small 0.15-mH inductance change across the operating range, again due to the copper shorting ring and overall motor construction.
Wavecor WF120BD04:
Klippel analysis for the Wavecor 4.75� woofer produced the Bl(X), Kms(X) and Bl and Kms symmetry range plots given in Figs. 22-25. The Bl(X) curve for the WF120 (Fig. 22) is relatively broad and symmetrical, especially for a 4.75� diameter driver, and obviously also with “tilt�? that includes a small forward (coil-out) offset. Looking at the Bl symmetry plot (Fig. 23), this curve shows a 0.8mm coil forward offset at the rest position that decreases to 0mm at the physical 4mm Xmax of the driver. Figures 24 and 25 show the Kms(X) and Kms symmetry range curves for the Wavecor midbass woofer.
The Kms(X) curve definitely has some asymmetry, and also with a minor rearward (coil-in) offset of about 0.8mm at the rest position that decreases to 0.25mm at the 4mm Xmax location on the graph, and increasing somewhat out to 6mm or so. While these numbers are small, it does limit the distortion levels somewhat. Displacement limiting numbers calculated by the Klippel analyzer were XBl at 82% Bl greater than 4.3mm and for XC at 75% Cms minimum was 2.3mm, which means that for this Wavecor woofer, the compliance is the most limit- ing factor for prescribed distortion level of 10%. This isn’t that much of an issue, especially because this woofer could easily find itself working as a midrange in a three-way product.
Figure 26 gives the inductance curve Le(X) for the WF120BD04. Inductance will typically increase in the rear direction from the zero rest position as the voice coil covers more pole area; however, the WF120 inductance stays most- ly constant as the coil moves in due to the dual shorting ring configuration. The inductance variation is only 0.05mH from the in and out Xmax positions, which is very good.